Ruth Kelty

Ruth Kelty

University of Maryland

Ruth is a recipient of a Curtis & Edith Munson Foundation award for coral reef research as well as a graduate intern at BBSR


My research indirectly examines how corals and sea anemones react to excess nutrients in the water. About 70% of all humans live within a few miles of water. Each time it rains, the water dissolves many chemicals produced by humans and transports them into nearby waters. In tropical areas such as many islands, chemicals called "nutrients" come from fertilizers and human sewage and re moved via surface flow (rivers) or by seeping into underground waters, flow out and pose a major threat to coral reefs.

The word "nutrients" basically means food to micro-organisms. The three main nutrients that are in all living things are carbon, nitrogen, and phosphorus (or C, N, and P). One of the few things that all life has in common is that it is made of carbon. Our hair, skin, muscles, and everything else that is or was once living has carbon in it. Nitrogen is used to build amino acids which are linked together to make proteins. DNA, the genetic material that determines what we look like, contains phosphorus. Phosphorus is also part of ATP (the P stands for phosphorus), the major energy source for the cell.

Corals are both animals and plants. Corals are animals that allow tiny algae cells to grow in-between their two cell layers. (To learn more about coral biology, click here). Imagine if you had a layer of algae growing under your skin! The algae likes to live there because it gets protected (to eat the algae you'd have to eat the coral animal too) and because it gets some leftover nutrients from the animal. The animal is healthier with the algae in it because the plant can give it carbon. Remember that when humans breath, we take in oxygen and breath out carbon dioxide. Plants do the opposite - they use carbon dioxide and release oxygen. (That is why we give plants to sick people.) If you had a plant living inside of you, you would have first dibbs on all of that carbon. This would mean that you wouldn't have to catch as much food (or eat so many twinkies) to get enough carbon to stay healthy.

Now that you know that corals are both plants and animals, how do you think corals will react to extra nitrogen and phosphorus? The plants should do well but the animal really cannot use the extra nutrients: it needs to get them from consuming plants (like you and broccoli). Although a fair amount of research has been done on the effect of nitrogen on corals, phosphorus has been neglected so I decided to focus my research on that!

I also want to know whether the animal or the algae decides how much phosphorus the coral will take from the water. If the animal lets the algae have as much as it wants, the algae may start growing so quickly that it will need to use all of its carbon for itself. One idea that I am testing is that the animal restricts the amount of phosphorus that the plant gets to control the plants growth. The interesting thing here is that if you take the algae away, the animal can only take up about a tenth of the phosphorus that it can with the algae present. So even though the animal may decide how much phosphorus the algae gets, the algae determines how much phosphorus the entire coral can take up.

In order to investigate these questions, I add radioactive phosphorus to the water surrounding the coral. Radioactivity can be measured in a scintillation counter that works using a chemical solution that makes bright light flash each time a radioactive particle releases some a packet of radiation (yes radiation comes in discreet packages!). The scintillation counter counts the number of flashes in each of my samples and converts that into a radioactive count per unit time. In order to find out where the phosphorus goes in a coral, I separate the animal and algae after the coral has been in the radioactive water for a few hours. Finally, I divide the animal and algae parts into four fractions, each containing the various chemical parts such as DNA, protein or lipids (fat).

My first set of experiments indicates that the animal gets almost all of the phosphorus and the algae get only a small amount.  This is contrary to the traditional view that the phosphorus would go into the algae, get attached to something like a lipid or small molecule and then be transferred to the animal. I will be posting more of my results as I go along so stop back later in the year to see how I have been progressing.

If you have any questions about my research, just email me!